Organic electroluminescent element, illuminator and display

ABSTRACT

An organic electroluminescent element containing an anode and a cathode having therebetween a light emitting layer containing a phosphorescent compound, and hole blocking layer 1 provided adjacent to the light emitting layer and between the light emitting layer and the cathode, wherein hole blocking layer 1 contains a phosphorescent compound; and a content of the phosphorescent compound contained in hole blocking layer 1 is in the range of 0.1 to 50% of a content of the phosphorescent compound contained in the light emitting layer.

This application is the United States national phase application ofInternational Application PCT/JP2004/010082 filed Jul. 8, 2004.

TECHNICAL FIELD

The present invention relates to an organic electroluminescent element,an illuminator and a display, and, in detail, relates to an organicelectroluminescent element, an illuminator and a display, exhibitinglong life.

BACKGROUND

As an emission type electronic displaying device, an electroluminescentdisplay (ELD) is known. Elements constituting the ELD include aninorganic electroluminescent element and an organic electroluminescentelement (hereinafter also referred to as an organic EL element).Inorganic electroluminescent elements have been used for a plane lightsource, however, a high voltage alternating current has been required todrive the element.

An organic EL element has a structure in which a light emitting layercontaining a light emitting compound is arranged between a cathode andan anode, and an electron and an electron hole are injected into thelight emitting layer and recombined to form an exciton. The elementemits light, utilizing light (fluorescent light or phosphorescent light)generated by inactivation of the exciton, and the element can emit lightby applying a relatively low voltage of several volts to several tens ofvolts. The element exhibits a wide viewing angle and a high visualitysince the element is self-luminous. Further, the element is a thin,completely solid element, and therefore, the element is noted from theviewpoint of space saving and portability.

A practical organic EL element is required to emit light of highluminance with high efficiency at a lower power. For example, disclosedare: an element exhibiting higher luminance of emitting light withlonger life in which stilbene derivatives, distyrylarylene derivativesor tristyrylarylene derivatives doped with a slight amount of afluorescent compound are employed (for example, see Patent Document 1);an element which has an organic light emitting layer containing an8-hydroxyquinoline aluminum complex as a host compound doped with aslight amount of a fluorescent compound (for example, see PatentDocument 2); and an element which has an organic light emitting layercontaining an 8-hydroxyquinoline aluminum complex as a host compounddoped with a quinacridone type dye (for example, see Patent Document 3).

When light emitted through excited singlet state is used in the organicEL elements disclosed in the above Patent Documents, the upper limit ofthe external quantum efficiency (ηext) is considered to be at most 5%,because the generation probability of excited species capable ofemitting light is 25%, since the generation ratio of singlet excitedspecies to triplet excited species is 1:3, and further, external lightemission efficiency is 20%.

Since an organic EL element, employing phosphorescence through theexcited triplet, was reported by Princeton University (for example, seeNon-Patent Document 1), studies on materials emitting phosphorescence atroom temperature have been actively carried out (for example, seeNon-Patent Document 2 and Patent Document 4). As the upper limit of theinternal quantum efficiency of the excited triplet is 100%, the lightemission efficiency of the exited triplet is theoretically four timesthat of the excited singlet. Accordingly, light emission employing theexcited triplet exhibits almost the same performance as a cold cathodetube, and can be applied to illumination.

In “The 10th International Workshop on Inorganic and OrganicElectroluminescence (EL '00, Hamamatsu)”, papers on phosphorescentcompounds have been reported. For example, Ikai et al. have reported aphosphorescent compound in which a hole transporting material had beenused as a host material. M. E. Thompson et al. have reported aphosphorescent compound of which the host material has been doped with anovel iridium complex compound. Tsutsui et al. have reported an organicEL element exhibiting high luminance by employing a hole blocking layer(an exciton blocking layer). Other examples of a hole blocking layerinclude: a kind of an aluminum complex reported by Pioneer Corp., and afluorine substituted compound as a hole blocking layer (an excitonblocking layer) exhibiting high luminance, reported by Ikai et al. inAppl. Phys. Lett., 70, 156 (2001).

Patent Document 1: Japanese Pat. No. 3093796

Patent Document 2: Japanese Patent Publication Open to Public Inspection(hereafter referred to as JP-A) No. 63-264692

Patent Document 3: JP-A No. 3-255190

Patent Document 4: JP-A No. 2000-21572

Non-Patent Document 1: M. A. Baldo et al., Nature, 395, 151-154 (1998)

Non-Patent Document 2: M. A. Baldo et al., Nature, 403(17), 750-753(2000)

However, in general, a phosphorescent element tends to exhibit a shorterlife time compared to a fluorescent element, and an organic EL elementemploying a phosphorescent compound as an emitting material is not fullydurable when it is continuously driven.

This may be due to the deterioration of a blocking layer provided toattain high luminance and a high emission efficiency.

Namely, electrons or holes drifted from the light emitting layer cannotbe fully blocked by the blocking layer and some of the electrons orholes migrate into the blocking layer, whereby the blocking layer isdeteriorated and the life of the element is shortened. Further, theexcitation life of a phosphorescent emission dopant is rather long,accordingly, when the concentration of excitons is high, a tripletexciton collides with another triplet exciton in the vicinity to causeT-T annihilation, whereby the emission efficiency is reduced.

The present invention was achieved under the above situations. An objectof the present invention is to provide an organic electroluminescentelement exhibiting long life and a high emission efficiency and, and toalso provide an illumination and a display employing the organicelectroluminescent element.

SUMMARY OF THE INVENTION

The above object of the present invention is achieved by the followingstructures.

(1) An organic electroluminescent element comprising an anode and acathode having therebetween a light emitting layer containing aphosphorescent compound, and hole blocking layer 1 provided adjacent tothe light emitting layer and between the light emitting layer and thecathode, wherein

hole blocking layer 1 contains a phosphorescent compound; and

a content of the phosphorescent compound contained in hole blockinglayer 1 is in the range of 0.1 to 50% of a content of the phosphorescentcompound contained in the light emitting layer.

(2). The organic electroluminescent element of Item (1), wherein theorganic electroluminescent element further contains hole blocking layer2 provided adjacent to hole blocking layer 1 and between hole blockinglayer 1 and the cathode.

(3) The organic electroluminescent element of Item (1) or Item (2),wherein the phosphorescent compound contained in the light emittinglayer is the same as the phosphorescent compound contained in holeblocking layer 1.

(4) The organic electroluminescent element of Item (1) or Item (2),wherein the phosphorescent compound contained in the light emittinglayer is different from the phosphorescent compound contained in holeblocking layer 1.

(5) An organic electroluminescent element comprising an anode and acathode having therebetween a light emitting layer containing aphosphorescent compound, and electron blocking layer 1 provided adjacentto the light emitting layer and between the light emitting layer and theanode, wherein

electron blocking layer 1 contains a phosphorescent compound; and

a content of the phosphorescent compound contained in electron blockinglayer 1 is in the range of 0.1 to 50% of a content of the phosphorescentcompound contained in the light emitting layer.

(6) The organic electroluminescent element of Item (5), wherein theorganic electroluminescent element further contains electron blockinglayer 2 provided adjacent to electron blocking layer 1 and betweenelectron blocking layer 1 and the anode.

(7) The organic electroluminescent element of Item (5) or Item (6),wherein the phosphorescent compound contained in the light emittinglayer is the same as the phosphorescent compound contained in electronblocking layer 1.

(8) The organic electroluminescent element of Item (5) or Item (6),wherein the phosphorescent compound contained in the light emittinglayer is different from the phosphorescent compound contained inelectron blocking layer 1.

(9) An organic electroluminescent element comprising an anode and acathode having therebetween a light emitting layer containing aphosphorescent compound; hole blocking layer 1 provided adjacent to thelight emitting layer and between the light emitting layer and thecathode; and electron blocking layer 1 provided adjacent to the lightemitting layer and between the light emitting layer and the anode,wherein

hole blocking layer 1 contains a phosphorescent compound;

a content of the phosphorescent compound contained in hole blockinglayer 1 is in the range of 0.1 to 50% of a content of the phosphorescentcompound contained in the light emitting layer;

electron blocking layer 1 contains a phosphorescent compound; and

a content of the phosphorescent compound contained in electron blockinglayer 1 is in the range of 0.1 to 50% of a content of the phosphorescentcompound contained in the light emitting layer.

(10) The organic electroluminescent element of Item (9), wherein theorganic electroluminescent element further contains hole blocking layer2 provided adjacent to hole blocking layer 1 and between hole blockinglayer 1 and the cathode.

(11) The organic electroluminescent element of Item (9) or Item (10),wherein the organic electroluminescent element further contains electronblocking layer 2 provided adjacent to electron blocking layer 1 andbetween electron blocking layer 1 and the anode.(12) The organic electroluminescent element of any one of Items(9)-(11), wherein the phosphorescent compound contained in the lightemitting layer is the same as the phosphorescent compound contained inhole blocking layer 1.(13) The organic electroluminescent element of any one of Items(9)-(11), wherein the phosphorescent compound contained in the lightemitting layer is different from the phosphorescent compound containedin hole blocking layer 1.(14) The organic electroluminescent element of any one of Items(9)-(12), wherein the phosphorescent compound contained in the lightemitting layer is the same as the phosphorescent compound contained inelectron blocking layer 1.(15) The organic electroluminescent element of any one of Items(9)-(11), wherein the phosphorescent compound contained in the lightemitting layer is different from the phosphorescent compound containedin electron blocking layer 1.(16) An organic electroluminescent element comprising an anode and acathode having therebetween a light emitting layer containing aphosphorescent compound, and hole blocking layer 1 provided adjacent tothe light emitting layer and between the light emitting layer and thecathode, wherein hole blocking layer 1 contains a phosphorescentcompound so that an amount of light emitted from hole blocking layer 1is in the range of 0.1 to 50% of an amount of light emitted from thelight emitting layer.(17) The organic electroluminescent element of Item (16), wherein theorganic electroluminescent element further contains hole blocking layer2 provided adjacent to hole blocking layer 1 and between hole blockinglayer 1 and the cathode.(18) An organic electroluminescent element comprising an anode and acathode having therebetween a light emitting layer containing aphosphorescent compound, and electron blocking layer 1 provided adjacentto the light emitting layer and between the light emitting layer and theanode, wherein electron blocking layer 1 contains a phosphorescentcompound so that an amount of light emitted from electron blocking layer1 is in the range of 0.1 to 50% of an amount of light emitted from thelight emitting layer.(19) The organic electroluminescent element of Item (18), wherein theorganic electroluminescent element further contains electron blockinglayer 2 provided adjacent to electron blocking layer 1 and betweenelectron blocking layer 1 and the anode.(20) An organic electroluminescent element comprising an anode and acathode having therebetween a light emitting layer containing aphosphorescent compound; hole blocking layer 1 provided adjacent to thelight emitting layer and between the light emitting layer and thecathode; and electron blocking layer 1 provided adjacent to the lightemitting layer and between the light emitting layer and the anode,wherein

hole blocking layer 1 contains a phosphorescent compound so that anamount of light emitted from hole blocking layer 1 is in the range of0.1 to 50% of an amount of light emitted from the light emitting layer;and

electron blocking layer 1 contains a phosphorescent compound so that anamount of light emitted from electron blocking layer 1 is in the rangeof 0.1 to 50% of an amount of light emitted from the light emittinglayer.

(21) The organic electroluminescent element of Item (20), wherein theorganic electroluminescent element further contains hole blocking layer2 provided adjacent to hole blocking layer 1 and between hole blockinglayer 1 and the cathode.

(22) The organic electroluminescent element of Item (20) or Item (21),wherein the organic electroluminescent element further contains electronblocking layer 2 provided adjacent to electron blocking layer 1 andbetween electron blocking layer 1 and the anode.(23) The organic electroluminescent element of any one of Items (1)-(22)emitting white light.(24) A display containing the organic electroluminescent element of anyone of Items (1)-(23).(25) An illumination device containing the organic electroluminescentelement of any one of Items (1)-(23).(26) A display containing a liquid crystal cell and the illuminationdevice of Item (25).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of one example of a display containing anorganic EL element.

FIG. 2 is a schematic drawing of a display section.

FIG. 3 is a schematic drawing of a pixel.

FIG. 4 is a schematic drawing of a display employing a passive matrixmethod.

FIG. 5 is a schematic drawing of an illumination.

FIG. 6 is a cross sectional view of an illumination.

BEST MODE TO CARRY OUT THE INVENTION

The present invention will now be detailed.

The inventors of the present invention, as a result of the examination,have found that an organic electroluminescent (EL) element exhibitinglong life and a high emission efficiency is obtained by an organicelectroluminescent element containing an anode and a cathode havingtherebetween a light emitting layer containing a phosphorescentcompound, and hole (electron hole) blocking layer 1 provided adjacent tothe light emitting layer and between the light emitting layer and thecathode, wherein hole blocking layer 1 contains a phosphorescentcompound; and the content of the phosphorescent compound contained inhole blocking layer 1 is in the range of 0.1 to 50% of the content ofthe phosphorescent compound contained in the light emitting layer.

Namely, the present inventors have found that, by controlling thecontent of the phosphorescent compound contained in hole blocking layer1 in the range of 0.1-50% of the content of the phosphorescent compoundcontained in the light emitting layer, the holes migrated into holeblocking layer 1 are stabilized, whereby deterioration of hole blockinglayer 1 is suppressed, and an elongation of the life of the organic ELelement is attained. Also found has been that, by enlarging therecombination area, the concentration of the triplet exciton is reducedand the occurrence of T-T annihilation is suppressed, whereby theemission efficiency is increased.

The present inventors have found that an organic electroluminescentelement exhibiting long life and a high emission efficiency is obtainedby an organic electroluminescent element containing an anode and acathode having therebetween a light emitting layer containing aphosphorescent compound, and electron blocking layer 1 provided adjacentto the light emitting layer and between the light emitting layer and theanode, wherein electron blocking layer 1 contains a phosphorescentcompound; and a content of the phosphorescent compound contained inelectron blocking layer 1 is in the range of 0.1 to 50% of a content ofthe phosphorescent compound contained in the light emitting layer.

Namely, the present inventors have found that, by controlling thecontent of the phosphorescent compound contained in electron blockinglayer 1 in the range of 0.1-50% of the content of the phosphorescentcompound contained in the light emitting layer, the electrons migratedinto electron blocking layer 1 is stabilized, whereby deterioration ofelectron blocking layer 1 is suppressed, and that an elongation of thelife of the organic EL element is attained. Also found has been that, byenlarging the recombination region, the concentration of the tripletexciton is reduced and the occurrence of T-T annihilation is suppressed,whereby the emission efficiency is increased.

Further, the present inventors have found that an organicelectroluminescent element exhibiting longer life and a higher emissionefficiency is obtained by an organic electroluminescent elementcomprising an anode and a cathode having therebetween a light emittinglayer containing a phosphorescent compound; hole blocking layer 1provided adjacent to the light emitting layer and between the lightemitting layer and the cathode; and electron blocking layer 1 providedadjacent to the light emitting layer and between the light emittinglayer and the anode, wherein hole blocking layer 1 contains aphosphorescent compound; the content of the phosphorescent compoundcontained in hole blocking layer 1 is in the range of 0.1 to 50% of thecontent of the phosphorescent compound contained in the light emittinglayer; electron blocking layer 1 contains a phosphorescent compound; andthe content of the phosphorescent compound contained in electronblocking layer 1 is in the range of 0.1 to 50% of the content of thephosphorescent compound contained in the light emitting layer.

The content of the phosphorescent compound contained in hole blockinglayer 1 is preferably in the range of 1 to 20% of the content of thephosphorescent compound contained in the light emitting layer, wherebyan organic electroluminescent element exhibiting longer life and ahigher emission efficiency is obtained. The content of thephosphorescent compound contained in electron blocking layer 1 ispreferably in the range of 1 to 20% of the content of the phosphorescentcompound contained in the light emitting layer, whereby an organicelectroluminescent element exhibiting longer life and a higher emissionefficiency is obtained.

In the present invention, the organic electroluminescent elementpreferably contains hole blocking layer 2 provided adjacent to holeblocking layer 1 and between hole blocking layer 1 and the cathode,whereby an organic electroluminescent element exhibiting longer life anda higher emission efficiency is obtained.

In the present invention, the organic electroluminescent elementpreferably contains electron blocking layer 2 provided adjacent toelectron blocking layer 1 and between hole blocking layer 1 and theanode, whereby an organic electroluminescent element exhibiting longerlife and a higher emission efficiency is obtained.

In the present invention, a hole blocking layer is a layer containing ahole blocking material, and it transports electrons to the lightemitting layer while suppressing effusion of holes from the lightemitting layer, whereby the recombination probability of holes withelectrons is increased.

A hole blocking material is a compound which has the role to block holes(electron holes) drifted from the light emitting layer and toefficiently transport electrons poured from the direction of the cathodeto the direction of the light emitting layer.

The properties desired for a hole blocking materials are as follows:

the following condition is satisfiedIp2−Ip1>Ez2−Ea1,provided that Ip1 and Ea1 represent the ionization potential and theelectron affinity of the light emitting layer, respectively, and Ip2 andEa2 represent the ionization potential and the electron affinity of thehole blocking layer, respectively; and

the energy of the excited triplet state of the hole blocking material islarger than the energy of the excited triplet state of the lightemitting layer.

Examples of a hole blocking material include complexes such as: a styrylcompound, a triazole derivative, a phenanthroline derivative, anoxydiazole derivative, a boron derivative, a carbazole derivative, asilole derivative, and an alminum complex.

As other examples of a hole blocking materials, the compounds disclosedin JP-A Nos. 2003-31367, 2003-31368 and Japanese Patent No. 2721441 arelisted.

Further listed as a hole blocking material are the following compounds:

An electron blocking layer is a layer containing an electron blockingmaterial, and it transports holes to the light emitting layer whilesuppressing effusion of electrons from the light emitting layer, wherebythe recombination probability of holes with electrons are increased.

An electron blocking material is a compound which has the roles to blockelectrons drifted from the light emitting layer and to efficientlytransport holes poured from the direction of the anode to the directionof the light emitting layer.

The properties desired for an electron blocking materials are asfollows:

the following condition is satisfiedEa1−Ea3>Ip1−Ip3,provided that Ip1 and Ea1 represent the ionization potential and theelectron affinity of the light emitting layer, respectively, and Ip3 andEa3 represent the ionization potential and the electron affinity of theelectron blocking layer, respectively; and

the energy of the excited triplet state of the electron blockingmaterial is larger than the energy of the excited triplet state of thelight emitting layer.

Ionization potential is defined as the energy required to emit anelectron in the HOMO (Highest Occupied Molecular Orbital) level of acompound to a vacuum level.

Specifically, it is the energy required to pick out an electron from thecompound of a membrane state (layer state), which can be measureddirectly by photoelectron spectroscopy, for example, by using ESCA 5600,UPS (ultraviolet photoemission spectroscopy), produced by ULVAC-PHI,INC.

Electron affinity is defined as the energy generated when an electron ina vacuum level falls in a LUMO (lowest unoccupied molecular orbital)level of a compound to be stabilized, and is obtained by the followingformula:Electron affinity (eV)=Ionization potential Ip (eV)+Band gap (eV)The band gap represents the energy of HOMO-LUMO of a compound, and canbe determined from the absorption edges of an absorption spectrum of amembrane formed on a quartz substrate.

As electron blocking materials, for example, a triarylamine derivativeand a carbazole derivative are listed.

The inventors of the present invention, as a result of the examination,have found that an organic electroluminescent (EL) element exhibitinglong life and a high emission efficiency is obtained by an organicelectroluminescent element comprising an anode and a cathode havingtherebetween a light emitting layer containing a phosphorescentcompound, and hole blocking layer 1 provided adjacent to the lightemitting layer and between the light emitting layer and the cathode,wherein hole blocking layer 1 contains a phosphorescent compound so thatthe amount of light emitted from hole blocking layer 1 is in the rangeof 0.1 to 50% of the amount of light emitted from the light emittinglayer.

Namely, the present inventors have found that, by controlling the amountof the phosphorescent compound contained in hole blocking layer 1 sothat the amount of light emitted from hole blocking layer 1 is in therange of 0.1 to 50% of the amount of light emitted from the lightemitting layer, the holes migrated into hole blocking layer 1 arestabilized by light emission from the light emitting material containedin hole blocking layer 1, whereby deterioration of hole blocking layer 1is suppressed, and an elongation of the life of the organic EL elementis attained. Also found has been that, by enlarging the recombinationregion, the concentration of the triplet exciton is reduced and theoccurrence of T-T annihilation is suppressed, whereby the emissionefficiency of the organic El element is increased.

The inventors of the present invention, as a result of the examination,have found that an organic electroluminescent (EL) element exhibitinglong life and a high emission efficiency is obtained by an organicelectroluminescent element comprising an anode and a cathode havingtherebetween a light emitting layer containing a phosphorescentcompound, and electron blocking layer 1 provided adjacent to the lightemitting layer and between the light emitting layer and the anode,wherein electron blocking layer 1 contains a phosphorescent compound sothat the amount of light emitted from electron blocking layer 1 is inthe range of 0.1 to 50% of the amount of light emitted from the lightemitting layer.

Namely, the present inventors have found that, by controlling the amountof the phosphorescent compound contained in electron blocking layer 1 sothat the amount of light emitted from electron blocking layer 1 is inthe range of 0.1 to 50% of the amount of light emitted from the lightemitting layer, the electrons migrated into electron blocking layer 1are stabilized by light emission from the light emitting materialcontained in electron blocking layer 1, whereby deterioration ofelectron blocking layer 1 is suppressed, and an elongation of the lifeof the organic EL element is attained. Also found has been that, byenlarging the recombination region, the concentration of the tripletexciton is reduced and the occurrence of T-T annihilation is suppressed,whereby the emission efficiency of the organic EL element is increased.

The inventors of the present invention, as a result of the examination,have found that an organic electroluminescent (EL) element exhibitinglonger life and a higher emission efficiency is obtained by an organicelectroluminescent element comprising an anode and a cathode havingtherebetween a light emitting layer containing a phosphorescentcompound; hole blocking layer 1 provided adjacent to the light emittinglayer and between the light emitting layer and the cathode; and electronblocking layer 1 provided adjacent to the light emitting layer andbetween the light emitting layer and the anode, wherein

hole blocking layer 1 contains a phosphorescent compound so that theamount of light emitted from hole blocking layer 1 is in the range of0.1 to 50% of the amount of light emitted from the light emitting layer;and

electron blocking layer 1 contains a phosphorescent compound so that theamount of light emitted from electron blocking layer 1 is in the rangeof 0.1 to 50% of the amount of light emitted from the light emittinglayer.

In hole blocking layer 1, the phosphorescent compound is preferablycontained so that the amount of light emitted from hole blocking layer 1is in the range of 3 to 50% of the amount of light emitted from thelight emitting layer, whereby an organic electroluminescent elementexhibiting longer life and a higher emission efficiency is obtained.

In electron blocking layer 1, the phosphorescent compound is preferablycontained so that the amount of light emitted from electron blockinglayer 1 is in the range of 3 to 50% of the amount of light emitted fromthe light emitting layer, whereby an organic electroluminescent elementexhibiting longer life and a higher emission efficiency is obtained.

Herein, phosphorescent light emission is measured by using electrolyticluminescence.

In the present invention, a phosphorescent compound is used as aluminescent material, whereby a high emission efficiency is acquired.

The phosphorescent compound of the present invention is suitably chosenfrom the known compounds used for the light emitting layer of theorganic EL element, examples of which include: iridium complexesdisclosed in JP-A No. 2001-247859 or in pp 16-18 of WO00/70,655; osmiumcomplexes; platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum complex. By using such a phosphorescent compoundas a dopant, an organic EL element exhibiting a high internal quantumefficiency is obtained. The phosphorescent compound used in the presentinvention is preferably a complex compound having a metal of Group 8 ofthe periodic table, and more preferably an iridium compound, an osmiumcompound, a platinum compound (a platinum complex compound), or a rareearth metal complex compound. Of these, most preferable is an iridiumcompound.

Examples of the phosphorescent compound used in the present inventionare shown below, however, the present invention is not limited thereto.These compounds can be prepared by a method, for example, reported inInorg. Chem., Vol 40, 1704-1711.

In addition to the above compounds, listed are the following compounds:iridium compounds represented by the formulas or listed as examples inJ. Am. Chem. Soc., Vol. 123, pp 4304-4312 (2001), WO00/70655,WO02/15645, JP-A No. 2001-247859, JP-A No. 2001-345183, JP-A No.2002-117978, JP-A No. 2002-170684, JP-A No. 2002-203678, JP-A No.2002-235076, JP-A No. 2002-302671, JP-A No. 2002-324679, JP-A No.2002-332291, JP-A No. 2002-332292 and JP-A No. 2002-338588; and theiridium complex represented by General Formula (IV) in JP-A No.2002-8860.

The phosphorescence quantum yield in a solution of the phosphorescentcompound of the present invention is 0.001 or more at 25° C., but it ispreferably 0.01 or more and furthermore preferably 0.1 or more.

The phosphorescence quantum yield can be measured according to a methoddescribed in the fourth edition “Jikken Kagaku Koza 7”, Bunko II, page398 (1992) published by Maruzen.

The constituting layers of the organic EL element of the presentinvention will be explained below in details.

Preferred examples of the constituting layers of the organic EL elementof the present invention will be shown below, however, the presentinvention is not limited thereto.

-   (1): Anode/Hole transport layer/Light emitting layer/Hole blocking    layer 1/Electron transport layer/Cathode-   (2): Anode/Hole transport layer/Light emitting layer/Hole blocking    layer 1/Hole blocking layer 2/Electron transport layer/Cathode-   (3): Anode/Hole transport layer/Electron blocking layer 1/Light    emitting layer/Electron transport layer/Cathode-   (4): Anode/Hole transport layer/Electron blocking layer 2/Electron    blocking layer 1/Light emitting layer/Electron transport    layer/Cathode-   (5): Anode/Hole transport layer/Electron blocking layer 1/Light    emitting layer/Hole blocking layer 1/Electron transport    layer/Cathode-   (6): Anode/Hole transport layer/Electron blocking layer 2/Electron    blocking layer 1/Light emitting layer/Hole blocking layer 1/Hole    blocking layer 2/Electron transport layer/Cathode-   (7): Anode/Anode buffer layer/Hole transport layer/Electron blocking    layer 2/Electron blocking layer 1/Light emitting layer/Hole blocking    layer 1/Hole blocking layer 2/Electron transport layer/Cathode    buffer layer/Cathode    <Anode>

For the anode of the organic EL element, a metal, an alloy, or anelectroconductive compound each having a high working function (not lessthan 4 eV), and mixture thereof are preferably used as the electrodematerial. Specific examples of such an electrode material include ametal such as Au, CuI and a transparent electroconductive material suchas indium tin oxide (ITO), SnO₂, or ZnO. A material capable of formingan amorphous and transparent conductive layer such as IDIXO (In₂O₃—ZnO)may also be used. The anode may be prepared by forming a thin layer ofthe electrode material according to a depositing or sputtering method,and by forming the layer into a desired pattern according to aphotolithographic method. When required precision of the pattern is notso high (not less than 100 μm), the pattern may be formed by depositingor sputtering of the electrode material through a mask having a desiredform. When light is emitted through the anode, the transmittance of theanode is preferably 10% or more, and the sheet resistance of the anodeis preferably not more than several hundred ohm/sq. The thickness of thelayer is ordinarily within the range of from 10 nm to 1 μm, andpreferably from 10 to 200 nm, although it may vary due to kinds ofmaterials used.

<Cathode>

On the other hand, for the cathode, a metal (also referred to as anelectron injecting metal), an alloy, and an electroconductive compoundeach having a low working function (not more than 4 eV), and a mixturethereof are used as the electrode material. Specific examples of such anelectrode material include sodium, sodium-potassium alloy, magnesium,lithium, a magnesium/copper mixture, a magnesium/silver mixture, amagnesium/aluminum mixture, a magnesium/indium mixture, analuminum/aluminum oxide (Al₂O₃) mixture, indium, a lithium/aluminummixture, and a rare-earth metal. Among them, a mixture of an electroninjecting metal and a metal higher in the working function than that ofthe electron injecting metal, such as the magnesium/silver mixture,magnesium/aluminum mixture, magnesium/indium mixture, aluminum/aluminumoxide (Al₂O₃) mixture, lithium/aluminum mixture, or aluminum is suitablefrom the view point of the electron injecting ability and resistance tooxidation. The cathode can be prepared forming a thin layer of such anelectrode material by a method such as a deposition or sputteringmethod. The sheet resistance as the cathode is preferably not more thanseveral hundred ohm/sq, and the thickness of the layer is ordinarilyfrom 10 nm to 1 μm, and preferably from 50 to 200 nm. It is preferablein increasing the light emission efficiency that either the anode or thecathode of the organic EL element is transparent or semi-transparent.

After a layer of the metal described above as a cathode is formed togive a thickness of from 1 to 20 nm, a layer of the transparentelectroconductive material as described in the anode is formed on theresulting metal layer, whereby a transparent or semi-transparent cathodecan be prepared. Employing the cathode, an element can be manufacturedin which both anode and cathode are transparent.

Next, an injection layer, a blocking layer, and an electron transportlayer used in the component layer of the organic EL element of thepresent invention will be explained.

<Buffer Layer>: Cathode Buffer layer, Anode Buffer Layer

The injection layer is optionally provided, for example, a cathodebuffer layer (an electron injection layer) or an anode buffer layer (ahole injection layer), and may be provided between the anode and thelight emitting layer or hole transport layer, and between the cathodeand the light emitting layer or electron transport layer as describedabove.

The buffer layer herein referred to is a layer provided between theelectrode and an organic layer in order to reduce the driving voltage orto improve of light emission efficiency. As the buffer layer there arean anode buffer layer and a cathode buffer layer, which are described in“Electrode Material” pages 123-166, Div. 2 Chapter 2 of “Organic ELelement and its frontier of industrialization” (published by NTSCorporation, Nov. 30, 1998) in detail.

The anode buffer layer (hole injection layer) is described in, forexample, JP-A Nos. 9-45479, 9-260062, and 8-288069, and its examplesinclude a phthalocyanine buffer layer represented by a copperphthalocyanine layer, an oxide buffer layer represented by a vanadiumoxide layer, an amorphous carbon buffer layer, and a polymer bufferlayer employing an electroconductive polymer such as polyaniline(emeraldine) and polythiophene.

The cathode buffer layer (an electron injection layer) is described in,for example, JP-A Nos. 6-325871, 9-17574, and 10-74586, in detail, andits examples include a metal buffer layer represented by a strontium oraluminum layer, an alkali metal compound buffer layer represented by alithium fluoride layer, an alkali earth metal compound buffer layerrepresented by a magnesium fluoride layer, and an oxide buffer layerrepresented by an aluminum oxide. The buffer layer (injection layer) ispreferably very thin and has a thickness of preferably from 0.1 to 5 μmdepending on kinds of the material used.

<Blocking Layer>: Hole Blocking layer, Electron Blocking Layer

The hole blocking layers are above described hole blocking layer 1 andhole blocking layer 2, both of which prevent effusion of holes from thelight emitting layer to obtain an organic EL element exhibiting highluminance and a high emission efficiency.

The electron blocking layers are above described electron blocking layer1 and electron blocking layer 2, both of which prevent effusion ofelectrons from the light emitting layer to obtain an organic EL elementexhibiting high liminance and a high emission efficiency.

<Light Emitting Layer>

The light emitting layer of the present invention contains aphosphorescent compound and it is a layer where injected electrons andholes are recombined to emit light. The portions where light is emittedmay be in the light emitting layer or at the interface between the lightemitting layer and the layer adjacent thereto.

By using a phosphorescent compound in the light emitting layer, anorganic EL element exhibiting a high emission efficiency is obtained.

As the phosphorescent compound, the above described compounds areusable.

The light emission of the phosphorescent compound is divided in twotypes in principle: one is an energy transfer type in whichrecombination of carriers occurs on the host compound to which thecarrier is transported to excite the host compound, the resulting energyis transferred to the phosphorescent compound and light is emitted fromthe phosphorescent compound; and the other is a carrier trap type inwhich recombination of carriers occurs on the phosphorescent compoundwhich works as a carrier trap material, and light is emitted from thephosphorescent compound. However, in each type, energy level of thephosphorescent compound in excited state is lower than that of the hostcompound in excited state.

In the present invention, the phosphorescence maximum wavelength of thephosphorescent compound is not specifically limited. Theoretically, thewavelength of the phosphorescence can be varied by selecting a centermetal, a ligand, or a substituent of the ligand. The phosphorescentcompound is preferably a phosphorescent compound having aphosphorescence maximum wavelength in the region of from 380 to 480 nm.As such organic electroluminescent elements, those emitting a blue orwhite light are listed.

When the same compound is used in each of the light emitting layer, holeblocking layer 1 and hole blocking layer 2, long life of the organic ELelement is attained without changing the emission spectrum, which is oneof the objects of the present invention.

The same effect can be obtained by using a different compound in thehole blocking layer or in the electron blocking layer from the compoundused in the light emitting layer, when the compounds exhibit the samecolor.

Further, by using a compound having a slightly different color in thehole blocking layer or in the electron blocking layer from the color ofthe compound used in the light emitting layer, an organic EL elementhaving a different color can be obtained.

Namely, use of a plurality of phosphorescent compounds enables to mixemissions of different colors and emission of an arbitrary color becomespossible. By adjusting the type and the amount of a phosphorescentcompound, emission of white light is possible, which enables to applythe organic EL element to an illuminator and to a backlight of adisplay.

In the present invention, white light emission may be used, which isobtained by changing the type and the amount of the phosphorescentcompound used in the hole blocking layer or in the electron blockinglayer, from the compound used in the light emitting layer.

The light emitting layer may also contain a host compound.

In the present invention, “host compound” is defined as a compound ofwhich phosphorescent quantum yield is less than 0.01.

In the present invention, as a host compound, above mentioned organic ELelement materials are preferably employed, whereby a higher emissionefficiency is obtained.

A plurality of host compounds known in the art may be used incombination. By using a plurality of host compound, charge transfer ismore easily controlled, whereby higher emission efficiency of an organicEL element is obtained.

Among those host compounds known in the art, preferable are those havinghole transporting ability, electron transport ability and a higher Tg (aglass transition temperature) value, while preventing elongation of theemission wavelength.

Examples of known host compound include the compounds disclosed in thefollowing documents:

JP-A Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491,2001-357977, 2002-334786, 2002-8860, 2002-334787, 2002-15871,2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579,2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683,2002-363227, 2002-231453, 2003-3165, 2002-234888, 2003-27048,2002-255934, 2002-260861, 2002-280183, 2002-299060, 2002-302516,2002-305083, 2002-305084 and 2002-308837.

Further, the following compounds are also listed as a host compound.

The light emitting layer may further contain a fluorescent compoundhaving a fluorescence maximum wavelength. In this case, by a energytransfer from other host compound or a phosphorescent compound to afluorescent compound, light emission from a host compound having afluorescence maximum wavelength is obtained as the result ofelectroluminescence of an organic EL element. The host compound having afluorescence maximum wavelength preferably has a high fluorescencequantum yield in the form of solution. Herein, the fluorescence quantumyield is preferably not less than 10%, and more preferably not less than30%. Examples of the a host compound having a wavelength providing afluorescence maximum wavelength include a coumarin dye, a cyanine dye, achloconium dye, a squalenium dye, an oxobenzanthracene dye, afluorescene dye, a rhodamine dye, a pyrylium dye, a perylene dye, astilbene dye, and a polythiophene dye. The fluorescence quantum yieldcan be measured according to a method described in the fourth edition,Jikken Kagaku Koza 7, Bunko II, p. 362 (1992) published by Maruzen.

Color of light emitted from the organic EL element or the compound ofthe present invention is measured by spectroradiometer CS-1000,manufactured by Minolta Co., Ltd., and expressed according to CIEchromaticity diagram described in FIG. 4.16 on page 108 of “ShinpenShikisai Kagaku Handbook” (Coloring Science Handbook, New Edition),edited by Nihon Shikisai Gakkai, published by Todai Shuppan Kai, 1985.

The light emitting layer can be formed employing the above-describedcompounds applied with a known method such as a vacuum depositionmethod, a spin coat method, a casting method, an LB method or an ink jetmethod. The thickness of the light emitting layer is not specificallylimited, however, it is ordinarily from 5 nm to 5 μm, and preferablyfrom 5 to 200 nm. The light emitting layer may be composed of a singlelayer containing one or more of phosphorescent compounds or hostcompounds, or may be composed of plural layers containing the samecomposition or different compositions.

<Hole Transport Layer>

The hole transport layer contains a hole transporting material having ahole transport ability. A hole injection layer and an electron blockinglayer are included in a hole transport layer in a broad sense. The holetransport layer may either be a single layer or a laminated layercontaining a plurality of layers.

“Hole transport material” means a compound having a hole injectionability, a hole transport ability or an electron blocking ability, andit may be an organic substance or an inorganic substance. Examples of ahole transport material include: a triazole derivative, an oxadiazolederivative, an imidazole derivative, a polyarylalkane derivative, apyrazoline derivative, a pyrazolone derivative, a phenylenediaminederivative, an arylamine derivative, an amino substituted chalconederivative, an oxazole derivative, a styrylanthracene derivative, afluorenone derivative, a hydrazone derivative, a stilbene derivative, asilazane derivative, an aniline copolymer, and an electroconductiveoligomer, specifically, a thiophene oligomer. As the hole transportingmaterial, those described above are used, however, a porphyrin compound,an aromatic tertiary amine compound and a styrylamine compound arepreferable, and, specifically, an aromatic tertiary amine compound ismore preferable.

Typical examples of the aromatic tertiary amine compound and styrylaminecompound include: N,N,N′,N′-tetraphenyl-4,4′-diaminophenyl,N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine(TPD), 2,2-bis(4-di-p-tolylaminophenyl)propane,1,1-bis(4-di-p-tolylaminophenyl)cyclohexane,N,N,N′,N′-tetra-p-tolyl-4,4′-diaminobiphenyl,1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane,bis(4-dimethylamino-2-methylphenyl)phenylmethane,bis(4-di-p-tolylaminophenyl)phenylmethane,N,N′-diphenyl-N,N′-di(4-methoxyphenyl)-4,4′-diaminobiphenyl,N,N,N′,N′-tetraphenyl-4,4′-diaminodiphenylether,4,4′-bis(diphenylamino)quardriphenyl, N,N,N-tri(p-tolyl)amine,4-(di-p-tolylamino)-4′-[4-(di-p-tolylamino)styryl]stilbene,4-N,N-diphenylamino-(2-diphenylvinyl)benzene,3-methoxy-4′-N,N-diphenylaminostylbene, N-phenylcarbazole, compoundsdescribed in U.S. Pat. No. 5,061,569 which have two condensed aromaticrings in the molecule thereof such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPD), and compoundsdescribed in JP-A No. 4-308688 such as4,4′,4′″-tris[N-(3-methylphenyl)-N-phenylamino]-triphenylamine (MTDATA)in which three triphenylamine units are bonded in a starburst form.

A polymer in which the material mentioned above is introduced in thepolymer chain or a polymer having the above mentioned material as thepolymer main chain can also be used. As a hole injecting material or ahole transport material, inorganic compounds such as p type-Si and ptype-SiC are usable.

The hole transport layer can be formed by preparing a thin layer of thehole transporting material using a known method such as a vacuumdeposition method, a spin coat method, a casting method, an ink jetmethod, and an LB method. The thickness of the hole transport layer isnot specifically limited, however, it is ordinarily from 5 nm to 5 μmand preferably 5-200 nm. The hole transport layer may be composed of asingle layer structure containing one or more of the materials mentionedabove.

<Electron Transport Layer>

The electron transport layer contains a material having an electrontransport ability, and in a broad sense an electron injection layer or ahole blocking layer are included in an electron transport layer. Theelectron transport layer can be provided as a single layer or as aplurality of layers.

The electron transport material is usable when it merely has a functionto transport electrons injected at the cathode to the light emittinglayer. Such electron transport materials may be optionally selected fromknown compounds used as electron transport materials, examples of whichinclude a nitro-substituted fluorene derivative, a diphenylquinonederivative, a thiopyran dioxide derivative, a carbodiimide, afluolenylidenemethane derivative, an anthraquinodimethane, an anthronederivative, and an oxadiazole derivative. Moreover, a thiadiazolederivative which is formed by substituting the oxygen atom in theoxadiazole ring of the foregoing oxadiazole derivative with a sulfuratom, and a quinoxaline derivative having a quinoxaline ring known as anelectron withdrawing group are usable as the electron transportmaterial.

A polymer in which the materials mentioned above are introduced in thepolymer side chain or a polymer having those materials as the polymermain chain are also applicable.

A metal complex of an 8-quinolynol derivative such as aluminumtris(8-quinolynol)(Alq), aluminum tris(5,7-dichloro-8-quinolynol),aluminum tris(5,7-dibromo-8-quinolynol), aluminumtris(2-methyl-8-quinolynol), aluminum tris(5-methyl-8-quinolynol), orzinc bis(8-quinolynol) (Znq), and a metal complex formed by replacingthe central metal of the foregoing complexes with another metal atomsuch as In, Mg, Cu, Ca, Sn, Ga or Pb, can be used as the electrontransporting material. Furthermore, a metal free or metal-containingphthalocyanine, and a derivative thereof, in which the molecularterminal is replaced by a substituent such as an alkyl group or asulfonic acid group, are also preferably used as the electrontransporting material. The distyrylpyrazine derivative exemplified as amaterial for the light emitting layer is preferably employed as theelectron transporting material. An inorganic semiconductor such as n-Siand n-SiC may also be used as the electron transporting material in away similar to the hole transport layer.

The electron transport layer can be formed employing the above describedelectron transporting materials and a known method such as a vacuumdeposition method, a spin coat method, a casting method, a printingmethod including an ink jet method or an LB method. The thickness ofelectron transport layer is not specifically limited, however, isordinarily from 5 nm to 5 μm, and preferably from 5 to 200 nm. Theelectron transport layer may be composed of a single layer containingone or two or more of the electron transporting material.

<Substrate (Also Referred to as Base Plate, Base or Support)>

The organic EL element of the present invention is preferably providedon a substrate.

The substrate employed for the organic electroluminescent element of thepresent invention is not restricted to specific kinds of materials suchas glass and plastic, as long as it is transparent. Examples of thesubstrate preferably used include glass, quartz and light transmissibleplastic film. Specifically preferred one is a resin film capable ofproviding flexibility to the organic EL element.

Examples of the resin film include films of polyethylene terephthalate(PET), polyethylene naphthalate (PEN), polyethersulfone (PES),polyetherimide, polyetheretherketone, polyphenylene sulfide,polyarylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC),cellulose acetate propionate (CAP). The surface of the resin film mayhave a layer of an inorganic or organic compound or a hybrid layer ofboth compounds.

The external light emission efficiency of the organic electroluminescentelement of the present invention is preferably not less than 1%, andmore preferably not less than 5% at room temperature. Herein, external:quantum yield (%) is represented by the following formula:External quantum yield (%)=((the number of photons emitted to theexterior of the organic electroluminescent element)/(the number ofelectrons supplied to the organic electroluminescent element))×100

A hue improving filter such as a color filter may be used in combinationor a color conversion filter which can convert emission light color froman organic EL element to multi-color employing a fluorescent compoundmay be used in combination. In the case where the color conversionfilter is used, the λmax of the light emitted from the organic ELelement is preferably not more than 480 nm.

<Preparation of Organic EL Element>

For one example, the preparation of the organic EL element, which hasthe following constitution will be described: Anode/Anode bufferlayer/Hole transport layer/Electron blocking layer 2/Electron blockinglayer 1/Light emitting layer/Hole blocking layer 1/Hole blocking layer2/Electron transport layer/Cathode buffer layer/Cathode

A thin layer of a desired material for an electrode such as a materialof the anode is formed on a suitable substrate by a vacuum deposition orsputtering method to prepare the anode so that the thickness of thelayer is not more than 1 μm and preferably within the range of from 10to 200 nm. Then organic compound thin layers including the anode bufferlayer, the hole transport layer, electron blocking layer 2, electronblocking layer 1, the light emitting layer, hole blocking layer 1, holeblocking layer 2, the electron transport layer, and the cathode bufferlayer, which constitute the organic EL element, are formed on theresulting anode in that order.

As methods for formation of the thin layers, as the same as describedabove, there are a vacuum deposition method and a wet process (forexample, a spin coating method, a casting method, an ink jet method, anda printing method), however, a vacuum deposition method, a spin coatingmethod, an ink jet method and a printing method are preferably used,since a uniform layer without a pinhole can be formed. Different methodsmay be used for formation of different layers. When the vacuumdeposition method is used for the thin layer formation method, althoughconditions of the vacuum deposition differs due to kinds of materialsused, vacuum deposition is preferably carried out at a boat temperatureof from 50° C. to 450° C., at a degree of vacuum of from 10⁻⁶ to 10⁻²Pa, at a deposition speed of from 0.01 to 50 nm/second, and at asubstrate temperature of from −50 to 300° C. to form a layer with athickness of from 0.1 nm to 5 μm, preferably from 5 to 200 nm.

After these layers has been formed, a thin layer of a material for acathode is formed thereon to prepare a cathode, employing, for example,a deposition method or sputtering method to give a thickness of not morethan 1 μm, and preferably from 50 to 200 nm. Thus, a desired organic ELelement is obtained. It is preferred that the layers from the holeinjection layer to the cathode are continuously formed under one time ofvacuuming to obtain an organic EL element. However, on the way of thelayer formation under vacuum, a different layer formation method bytaking the layer out of the vacuum chamber may be inserted. When thedifferent method is used, the process is required to be carried outunder a dry inert gas atmosphere.

In the multicolor display of the present invention, the light emittinglayer only is formed using a shadow mask, and the other layers, besidesthe light emitting layer, are formed employing a vacuum method, acasting method, a spin coating method, an ink-jetting method or aprinting method in which patterning employing the shadow mask is notrequired.

When the light emitting layer only is formed by patterning, the layerformation, although not specifically limited, is carried out preferablyaccording to a vacuum deposition method, an ink jet method or a printingmethod. When a vacuum deposition method is used as the layer formationmethod, patterning of the layer is preferably carried out employing ashadow mask.

Further, the organic EL element can be prepared in the reverse order.When a direct current voltage, a voltage of 2 to 40 V is applied to thusobtained multicolor display, setting the anode as a + polarity and thecathode as a − polarity, light emission occurs. An alternating currentmay also be applied to cause light emission. Arbitrary wave shape ofalternating current may be used.

The display of the present invention can be used as a display device, adisplay, or various light emission sources. The display device or thedisplay, which employs three kinds of organic EL elements emitting ablue light, a red light and a green light can present a full colorimage.

Examples of the display device or the display include a television, apersonal computer, a mobile device or an AV device, a display for textbroadcasting, and an information display used in a car. The displaydevice may be used as specifically a display for reproducing a stillimage or a moving image. When the display device is used as a displayfor reproducing a moving image, the driving method may be either asimple matrix (passive matrix) method or an active matrix method.

Examples of an illuminator include a home lamp, a room lamp in a car, abacklight for a watch or a liquid crystal, a light source for boardingadvertisement, a signal device, a light source for a photo memorymedium, a light source for an electrophotographic copier, a light sourcefor an optical communication instrument, and a light source for anoptical sensor, however, are not limited thereto.

The organic EL element of the present invention may be an organic ELelement having a resonator structure.

The organic EL element having a resonator structure is applied to alight source for a photo-memory medium, a light source for anelectrophotographic copier, a light source for an optical communicationinstrument, or a light source for a photo-sensor, however, itsapplication is not limited thereto. In the above application, a laseroscillation may be carried out.

<Display>

The organic EL element of the present invention can be used as a lampsuch as an illuminating lamp or a light source for exposure, as aprojection device for projecting an image, or as a display for directlyviewing a still image or a moving image. When the element is used in adisplay for reproducing a moving image, the driving method may be eithera simple matrix (passive matrix) method or an active matrix method. Thedisplay can present a full color image by employing two or more kinds oforganic EL elements each emitting light with a different color. Amonochromatic color, for example, a white color can be converted to afull color of BGR, employing a color filter. Further, employing a colorconversion filter, light color emitted from the organic EL element canbe converted to another color or full color, where the λmax of the lightemitted from the organic EL element is preferably not more than 480 nm.

One of the examples of the display containing the organic EL element ofthe present invention will be explained below employing figures.

FIG. 1 is a schematic drawing of one example of a display containing anorganic EL element. FIG. 1 is a display such as that of a cellularphone, displaying image information due to light emission from theorganic EL.

Display 1 contains display section A having plural pixels and controlsection B carrying out image scanning based on image information todisplay an image in display section A.

Control section B is electrically connected to display section A,transmits a scanning signal and an image data signal to each of theplural pixels based on image information from the exterior, and conductsimage scanning which emits light from each pixel due to the scanningsignal according to the image data signal, whereby an image is displayedon display section A.

FIG. 2 is a schematic drawing of display section A. Display section Acontains a substrate, plural pixels 3, and a wiring section containingplural scanning lines 5 and plural data lines 6. The main members ofdisplay section A will be explained below. In FIG. 2, light from pixels3 is emitted in the direction of an arrow.

Plural scanning lines 5 and plural data lines 6 of wiring section 2 eachare composed of an electroconductive material, lines 5 and lines 6 beingcrossed with each other at a right angle, and connected with pixels 3 atthe crossed points (not illustrated).

Plural pixels 3, when the scanning signal is applied from scanning lines5, receive the data signal from data lines 6, and emit lightcorresponding to the image data received. Provision of red lightemitting pixels, green light emitting pixels, and blue light emittingpixels side by side on the same substrate can display a full colorimage.

Next, an emission process of pixels will be explained.

FIG. 3 is a schematic drawing of a pixel.

The pixel contains organic EL element 10, switching transistor 11,driving transistor 12, and capacitor 13. When a pixel with a red lightemitting organic EL element, a pixel with a green light emitting organicEL element, and a pixel with a blue light emitting organic EL elementare provided side by side on the same substrate, a full color image canbe displayed.

In FIG. 3, an image data signal is applied through data lines 6 fromcontrol section B to a drain of switching transistor 11, and when ascanning signal is applied to a gate of switching transistor 11 throughscanning lines 5 from control section B, switching transistor 11 isswitched on, and the image signal data applied to the drain istransmitted to capacitor 13 and the gate of driving transistor 12.

Capacitor 13 is charged according to the electric potential of the imagedata signal transmitted, and driving transistor 12 is switched on. Indriving transistor 12, the drain is connected to electric source line 7,and the source to organic EL element 10. Current is supplied fromelectric source line 7 to organic EL element 10 according to theelectric potential of the image data signal applied to the gate.

The scanning signal is transmitted to next scanning line 5 according tothe successive scanning of control section B, switching transistor 11 isswitched off. Even if switching transistor 11 is switched off, drivingtransistor 12 is turned on since capacitor 13 maintains a chargedpotential of image data signal, and light emission from organic ELelement 10 continues until the next scanning signal is applied. When thenext scanning signal is applied according the successive scanning,driving transistor 12 works according to an electric potential of thenext image data signal synchronized with the scanning signal, and lightis emitted from organic EL element 10.

That is, light is emitted from organic EL element 10 in each of pluralpixels 3 due to switching transistor 11 as an active element and drivingtransistor 12 each being provided in organic EL element 10 of each ofplural pixels 3. This emission process is called an active matrixprocess.

Herein, light emission from organic EL element 10 may be emission withplural gradations according to image signal data of multiple valuehaving plural gradation potentials, or emission due to on-off accordingto a binary value of the image data signals.

The electric potential of capacitor 13 may maintain till the nextapplication of the scanning signal, or may be discharged immediatelybefore the next scanning signal is applied.

In the present invention, light emission may be carried out employing apassive matrix method as well as the active matrix method as describedabove. The passive matrix method is one in which light is emitted fromthe organic EL element according to the data signal only when thescanning signals are scanned.

FIG. 4 is a schematic drawing of a display employing a passive matrixmethod. In FIG. 4, pixels 3 are provided between scanning lines 5 anddata lines 6, crossing with each other.

When scanning signal is applied to scanning line 5 according tosuccessive scanning, pixel 3 connecting scanning line 5 emits accordingto the image data signal. The passive matrix method has no activeelement in pixel 3, which reduces manufacturing cost of a display.

EXAMPLES

The present invention will now be explained using the examples, however,the present invention is not limited thereto.

Example 1 Preparation of Organic EL Elements 1-1 to 1-10

(1) Preparation of Organic EL Element 1-1

A pattern was formed on a substrate (100 mm×100 mm×1.1 mm) composed of aglass plate and a 100 nm ITO (indium tin oxide) layer (NA45 manufacturedby NH Technoglass. Co., Ltd.) as an anode. Then the resultingtransparent substrate having the ITO transparent electrode was subjectedto ultrasonic washing in i-propyl alcohol and dried with a dry nitrogengas and subjected to UV-ozone cleaning for 5 minutes. Thus obtainedtransparent substrate was fixed on a substrate holder of a vacuumdeposition apparatus available on the market. Further, 200 mg of NPD wasplaced in a resistive heating molybdenum boat, 200 mg of CBP was put inanother resistive heating molybdenum boat, 200 mg of Ir-1 was placed inanother resistive heating molybdenum boat, 200 mg of bathocuproine (BCP)was placed in another resistive heating molybdenum boat, and 200 mg ofAlq₃ was placed in another resistive heating molybdenum boat, and thenfixed in the vacuum deposition apparatus.

The pressure in the vacuum tank was reduced to 4×10⁻⁴ Pa. Then, the boatcarrying NPD was heated by supplying an electric current to the boat,and NPD was deposited onto the transparent substrate at a depositingspeed of 0.1 nm/sec to form a 45 nm thick hole transport layer. Afterthat, the boat carrying CBP and the boat carrying Ir-1 were heated bysupplying an electric current to both boats, and CBP at a depositingspeed of 0.1 nm/sec and Ir-1 at a depositing speed of 0.006 nm/sec wereco-deposited onto the resulting hole transport layer to form a lightemitting layer with a thickness of 30 nm.

Subsequently, the boat carrying BCP and the boat carrying Ir-1 wereheated by supplying an electric current to the boats, and BCP at adepositing speed of 0.2 nm/sec and Ir-1 at a depositing speed of 0.0001nm/sec were co-deposited onto the resulting light emitting layer to formhole blocking layer 1 with a thickness of 20 nm.

Further, the boat carrying Alq₃ was heated by supplying an electriccurrent to the boat, and Alq₃ was deposited onto the resulting holeblocking layer 1 at a depositing speed of 0.1 nm/sec to form an electrontransport layer with a thickness of 30 nm. The temperature of thesubstrate at the time of the deposition was room temperature.

After that, a 0.5 nm thick lithium fluoride layer as a cathode bufferlayer and a 110 nm thick aluminum layer as a cathode were deposited.Thus, Organic EL Element 1-1 was prepared.

(2) Preparation of Organic EL Element 1-2

Organic EL Element 1-2 was prepared in the same manner as Organic ELElement 1-1 except that only BCP was deposited without using Ir-1 toform hole blocking layer 1 (with a deposition speed: 0.2 nm/sec and athickness: 20 nm).

(3) Preparation of Organic EL Element 1-3

A pattern was formed on a substrate (100 mm×100 mm×1.1 mm) composed of aglass plate and a 100 nm ITO (indium tin oxide) layer (NA45 manufacturedby NH Technoglass Co., Ltd.) as an anode. Then the resulting transparentsubstrate having the ITO transparent electrode was subjected toultrasonic washing in i-propyl alcohol and dried with a dry nitrogen gasand subjected to UV-ozone cleaning for 5 minutes. Thus obtainedtransparent substrate was fixed on a substrate holder of a vacuumdeposition apparatus available on the market. Further, 200 mg of NPD wasplaced in a resistive heating molybdenum boat, 200 mg of compound 1 wasplaced in another resistive heating molybdenum boat, 200 mg of compound2 was placed in another resistive heating molybdenum boat, 100 mg ofIr-12 was placed in another resistive heating molybdenum boat, 200 mg ofcompound 3 was placed in another resistive heating molybdenum boat, and200 mg of Alq₃ was placed in another resistive heating molybdenum boat,and then fixed in the vacuum deposition apparatus.

The pressure in the vacuum tank was reduced to 4×10⁻⁴ Pa. Then, the boatcarrying NPD was heated by supplying an electric current to the boat,and NPD was deposited onto the transparent substrate at a depositingspeed of 0.1 nm/sec to form a 25 nm thick hole transport layer.

After that, the boat carrying compound 1 and the boat carrying Ir-12were heated by supplying an electric current to both boats, and compound1 at a depositing speed of 0.2 nm/sec and Ir-12 at a depositing speed of0.0004 nm/sec were co-deposited onto the resulting hole transport layerto form electron blocking layer 1 with a thickness of 20 nm.

Subsequently, the boat carrying compound 2 and the boat carrying Ir-12were heated by supplying an electric current to the boats, and compound2 at a depositing speed of 0.1 nm/sec and Ir-12 at a depositing speed of0.006 nm/sec were co-deposited onto the resulting electron blockinglayer 1 to form a light emitting layer with a thickness of 30 nm.

Then, the boat carrying compound 3 and the boat carrying Ir-12 wereheated by supplying an electric current to the boats, and compound 3 ata depositing speed of 0.2 nm/sec and Ir-12 at a depositing speed of0.0001 nm/sec were co-deposited onto the resulting light emitting layerto form a hole blocking layer 1 with a thickness of 20 nm.

Further, the boat carrying Alq₃ was heated by supplying an electriccurrent to the boat, and Alq₃ was deposited onto the resulting holeblocking layer 1 at a depositing speed of 0.1 nm/sec to form an electrontransport layer with a thickness of 30 nm. The temperature of thesubstrate at the time of the deposition was room temperature.

After that, a 0.5 nm thick lithium fluoride layer as a cathode bufferlayer and a 110 nm thick aluminum layer as a cathode were deposited.Thus, Organic EL Element 1-3 was prepared.

(4) Preparation of Organic EL Element 1-4

A pattern was formed on a substrate (100 mm×10.0 mm×1.1 mm) composed ofa glass plate and a 100 nm ITO (indium tin oxide) layer (NA45manufactured by NH Technoglass Co., Ltd.) as an anode. Then theresulting transparent substrate having the ITO transparent electrode wassubjected to ultrasonic washing in i-propyl alcohol and dried with a drynitrogen gas and subjected to UV-ozone cleaning for 5 minutes. Thusobtained transparent substrate was fixed on a substrate holder of avacuum deposition apparatus available on the market. Further, 200 mg ofNPD was placed in a resistive heating molybdenum boat, 200 mg ofcompound 1 was placed in another resistive heating molybdenum boat, 200mg of compound 2 was placed in another resistive heating molybdenumboat, 100 mg of Ir-12 was placed in another resistive heating molybdenumboat, 200 mg of compound 3 was placed in another resistive heatingmolybdenum boat, and 200 mg of Alq₃ was placed in another resistiveheating molybdenum boat, and then fixed in the vacuum depositionapparatus.

The pressure in the vacuum tank was reduced to 4×10⁻⁴ Pa. Then, the boatcarrying NPD was heated by supplying an electric current to the boat,and NPD was deposited onto the transparent substrate at a depositingspeed of 0.1 nm/sec to form a 25 nm thick hole transport layer.

After that, the boat carrying Compound 1 was heated by supplying anelectric current to the boat, and Compound 1 was deposited at adepositing speed of 0.1 nm/sec onto the resulting hole transport layerto form electron blocking layer 2 with a thickness of 10 nm.

Subsequently, the boat carrying Compound 1 and the boat carrying Ir-12were heated by supplying an electric current to the boats, and compound1 at a depositing speed of 0.2 nm/sec and Ir-12 at a depositing speed of0.0004 nm/sec were co-deposited onto the resulting electron blockinglayer 2 to form electron blocking layer 1 with a thickness of 10 nm.

Then, the boat carrying compound 2 and the boat carrying Ir-12 wereheated by supplying an electric current to the boats, and compound 2 ata depositing speed of 0.1 nm/sec and Ir-12 at a depositing speed of0.006 nm/sec were co-deposited onto the resulting electron blockinglayer 1 to form a light emitting layer with a thickness of 30 nm.

Then, the boat carrying compound 3 and the boat carrying Ir-12 wereheated by supplying an electric current to the boats, and compound 3 ata depositing speed of 0.2 nm/sec and Ir-12 at a depositing speed of0.0001 nm/sec were co-deposited onto the resulting light emitting layerto form hole blocking layer 1 with a thickness of 10 nm.

After that, the boat carrying compound 3 was heated by supplying anelectric current to the boat, and compound 3 was deposited onto theresulting hole blocking layer 1 to form hole blocking layer 2 with athickness of 10 nm.

Then, the boat carrying Alq₃ was heated by supplying an electric currentto the boat, and Alq₃ was deposited onto the resulting hole blockinglayer 2 at a depositing speed of 0.1 nm/sec to form an electrontransport layer with a thickness of 30 nm. The temperature of thesubstrate at the time of the deposition was room temperature.

After that, a 0.5 nm thick lithium fluoride layer as a cathode bufferlayer and a 110 nm thick aluminum layer as a cathode were deposited.Thus, Organic EL Element 1-4 was prepared.

(5) Preparation of Organic EL Element 1-5

Organic EL Element 1-5 was prepared in the same manner as Organic ELElement 1-3 except that only compound 1 was deposited without usingIr-12 to form electron blocking layer 1 (with a deposition speed: 0.2nm/sec and a thickness: 20 nm), and that only compound 3 was depositedwithout using Ir-12 to form hole blocking layer 1 (with a depositionspeed: 0.2 nm/sec and a thickness: 20 nm).

(6) Preparation of Organic EL Element 1-6

A pattern was formed on a substrate (100 mm×100 mm×1.1 mm) composed of aglass plate and a 100 nm ITO (indium tin oxide) layer (NA45 manufacturedby NH Technoglass Co., Ltd.) as an anode. Then the resulting transparentsubstrate having the ITO transparent electrode was subjected toultrasonic washing in i-propyl alcohol and dried with a dry nitrogen gasand subjected to UV-ozone cleaning for 5 minutes. Thus obtainedtransparent substrate was fixed on a substrate holder of a vacuumdeposition apparatus available on the market. Further, 200 mg of NPD wasplaced in a resistive heating molybdenum boat, 200 mg of compound 1 wasplaced in another resistive heating molybdenum boat, 200 mg of compound2 was placed in another resistive heating molybdenum boat, 100 mg ofIr-1 was placed in another resistive heating molybdenum boat, 100 mg ofIr-12 was placed in another resistive heating molybdenum boat, 100 mg ofIr-7 was placed in another resistive heating molybdenum boat, 200 mg ofcompound 3 was placed in another resistive heating molybdenum boat, and200 mg of Alq₃ was placed in another resistive heating molybdenum boat,and then fixed in the vacuum deposition apparatus.

The pressure in the vacuum tank was reduced to 4×10⁻⁴ Pa. Then, the boatcarrying NPD was heated by supplying an electric current to the boat,and NPD was deposited onto the transparent substrate at a depositingspeed of 0.1 nm/sec to form a 25 nm thick hole transport layer.

After that, the boat carrying compound 1 was heated by supplying anelectric current to the boat, and compound 1 was deposited at adepositing speed of 0.1 nm/sec onto the resulting hole transport layerto form electron blocking layer 2 with a thickness of 10 nm.

Subsequently, the boat carrying compound 1 and the boat carrying Ir-12were heated by supplying an electric current to the boats, and compound1 at a depositing speed of 0.1 nm/sec and Ir-12 at a depositing speed of0.0006 nm/sec were co-deposited onto the resulting electron-blockinglayer 2 to form electron blocking layer 1 with a thickness of 10 nm.

Then, the boat carrying compound 2 and the boat carrying Ir-1 wereheated by supplying an electric current to the boats, and compound 2 ata depositing speed of 0.1 nm/sec and Ir-12 at a depositing speed of0.006 nm/sec were co-deposited onto the resulting electron blockinglayer 1 to form a light emitting layer with a thickness of 30 nm.

Then, the boat carrying compound 3 and the boat carrying Ir-7 wereheated by supplying an electric current to the boats, and compound 3 ata depositing speed of 0.1 nm/sec and Ir-7 at a depositing speed of0.0003 nm/sec were co-deposited onto the resulting light emitting layerto form hole blocking layer 1 with a thickness of 10 nm.

After that, the boat carrying compound 3 was heated by supplying anelectric current to the boat, and compound 3 was deposited onto theresulting hole blocking layer 1 to form hole blocking layer 2 with athickness of 10 nm.

Then, the boat carrying Alq₃ was heated by supplying an electric currentto the boat, and Alq₃ was deposited onto the resulting hole blockinglayer 2 at a depositing speed of 0.1 nm/sec to form an electrontransport layer with a thickness of 30 nm. The temperature of thesubstrate at the time of the deposition was room temperature.

After that, a 0.5 nm thick lithium fluoride layer as a cathode bufferlayer and a 110 nm thick aluminum layer as a cathode were deposited.Thus, Organic EL Element 1-6 was prepared.

(7) Preparation of Organic EL Element 1-7

A pattern was formed on a substrate (100 mm×100 mm×1.1 mm) composed of aglass plate and a 100 nm ITO (indium tin oxide) layer (NA45 manufacturedby NH Technoglass Co., Ltd.) as an anode. Then the resulting transparentsubstrate having the ITO transparent electrode was subjected toultrasonic washing in i-propyl alcohol and dried with a dry nitrogen gasand subjected to UV-ozone cleaning for 5 minutes. Thus obtainedtransparent substrate was fixed on a substrate holder of a vacuumdeposition apparatus available on the market. Further, 200 mg of NPD wasplaced in a resistive heating molybdenum boat, 200 mg of compound 1 wasplaced in another resistive heating molybdenum boat, 200 mg of compound2 was placed in another resistive heating molybdenum boat, 100 mg ofIr-1 was placed in another resistive heating molybdenum boat, 100 mg ofIr-12 was placed in another resistive heating molybdenum boat, 100 mg ofIr-7 was placed in another resistive heating molybdenum boat, 200 mg ofcompound 3 was placed in another resistive heating molybdenum boat, and200 mg of Alq₃ was placed in another resistive heating molybdenum boat,and then fixed in the vacuum deposition apparatus.

The pressure in the vacuum tank was reduced to 4×10⁻⁴ Pa. Then, the boatcarrying NPD was heated by supplying an electric current to the boat,and NPD was deposited onto the transparent substrate at a depositingspeed of 0.1 nm/sec to form a 25 nm thick hole transport layer.

After that, the boat carrying compound 1 was heated by supplying anelectric current to the boat, and compound 1 was deposited at adepositing speed of 0.1 nm/sec onto the resulting hole transport layerto form electron blocking layer 1 with a thickness of 20 nm.

Subsequently, the boat carrying compound 2, the boat carrying Ir-1 andthe boat carrying Ir-12 were heated by supplying an electric current tothe boats, and compound 2 at a depositing speed of 0.1 nm/sec, Ir-1 at adepositing speed of 0.004 nm/sec, and Ir-12 at a depositing speed of0.003 nm/sec were co-deposited onto the resulting electron blockinglayer 1 to form a light emitting layer with a thickness of 30 nm.

Then, the boat carrying compound 3 and the boat carrying Ir-7 wereheated by supplying an electric current to the boats, and compound 3 ata depositing speed of 0.1 nm/sec and Ir-7 at a depositing speed of0.0003 nm/sec were co-deposited onto the resulting light emitting layerto form hole blocking layer 1 with a thickness of 10 nm.

After that, the boat carrying compound 3 was heated by supplying anelectric current to the boat, and compound 3 was deposited onto theresulting hole blocking layer 1 to form hole blocking layer 2 with athickness of 10 nm.

Then, the boat carrying Alq₃ was heated by supplying an electric currentto the boat, and Alq₃ was deposited onto the resulting hole blocking,layer 2 at a depositing speed of 0.1 nm/sec to form an electrontransport layer with a thickness of 30 nm. The temperature of thesubstrate at the time of, the deposition was room temperature.

After that, a 0.5 nm thick lithium fluoride layer as a cathode bufferlayer and a 110 nm thick aluminum layer as a cathode were deposited.Thus, Organic EL Element 1-7 was prepared.

(8) Preparation of Organic EL Element 1-8

A pattern was formed on a substrate (100 mm×100 mm×1.1 mm) composed of aglass plate and a 100 nm ITO (indium tin oxide) layer (NA45 manufacturedby NH Technoglass Co., Ltd.) as an anode. Then the resulting transparentsubstrate having the ITO transparent electrode was subjected toultrasonic washing in i-propyl alcohol and dried with a dry nitrogen gasand subjected to UV-ozone cleaning for 5 minutes. Thus obtainedtransparent substrate was fixed on a substrate holder of a vacuumdeposition apparatus available on the market. Further, 200 mg of NPD wasplaced in a resistive heating molybdenum boat, 200 mg of compound 1 wasplaced in another resistive heating molybdenum boat 200 mg of compound 2was placed in another resistive heating molybdenum boat, 100 mg of Ir-1was placed in another resistive heating molybdenum boat, 100 mg of Ir-12was placed in another resistive heating molybdenum boat, 100 mg of Ir-7was placed in another resistive heating molybdenum boat, 200 mg ofcompound 3 was placed in another resistive heating molybdenum boat, and200 mg of Alq₃ was placed in another resistive heating molybdenum boat,and then fixed in the vacuum deposition apparatus.

The pressure in the vacuum tank was reduced to 4×10⁻⁴ Pa. Then, the boatcarrying NPD was heated by supplying an electric current to the boat,and NPD was deposited onto the transparent substrate at a depositingspeed of 0.1 nm/sec to form a 25 nm thick hole transport layer.

After that, the boat carrying compound 1 was heated by supplying anelectric current to the boat, and compound 1 was deposited at adepositing speed of 0.1 nm/sec onto the resulting hole transport layerto form electron blocking layer 1 with a thickness of 20 nm.

Subsequently, the boat carrying compound 2, the boat carrying Ir-1, theboat carrying Ir-7, and the boat carrying Ir-12 were heated by supplyingan electric current to the boats, and compound 2 at a depositing speedof 0.1 nm/sec, Ir-1 at a depositing speed of 0.004 nm/sec, Ir-7 at adepositing speed of 0.003 nm/sec, and Ir-12 at a depositing speed of0.002 nm/sec were co-deposited onto the resulting electron blockinglayer 1 to form a light emitting layer with a thickness of 30 nm.

After that, the boat carrying compound 3 was heated by supplying anelectric current to the boat, and compound 3 was deposited at adepositing speed of 0.1 nm/sec onto the light emitting layer to formhole blocking layer 1 with a thickness of 10 nm.

After that, the boat carrying compound 3 was heated by supplying anelectric current to the boat, and compound 3 was deposited onto theresulting hole blocking layer 1 to form hole blocking layer 2 with athickness of 10 nm.

Then, the boat carrying Alq₃ was heated by supplying an electric currentto the boat, and Alq₃ was deposited onto the resulting hole blockinglayer 2 at a depositing speed of 0.1 nm/sec to form an electrontransport layer with a thickness of 30 nm. The temperature of thesubstrate at the time of the deposition was room temperature.

After that, a 0.5 nm thick lithium fluoride layer as a cathode bufferlayer and a 110 nm thick aluminum layer as a cathode were deposited.Thus, organic EL Element 1-8 was prepared.

(9) Preparation of Organic EL Element 1-9

Construction of the element:

-   -   ITO/NPD/CBP:rubrene/BCP:rubrene/Alq₃/LiF/Al

Preparation method is the same as that of Organic EL Element 1-1,wherein the dopant is rubrene which is a fluorescent dopant.

(10) Preparation of Organic EL Element 1-10

Construction of the element:

-   -   ITO/NPD/CBP:rubrene/BCP/Alq₃/LiF/Al

An example of Organic EL Element 1-9, in which rubrene is not used inthe hole blocking layer.

Preparation method is the same as that of Organic EL Element 1-2,wherein the dopant of the light emitting layer is rubrene which is afluorescent dopant.

Preparation method is the same as that of Organic EL Element 1-2,wherein the dopant is rubrene which is a fluorescent dopant.

With respect to prepared Organic EL Element 1-1 to 1-10, the data oncolor of emitted light; the content of the phosphorescent compound inhole blocking layer 1, electron blocking layer 1 and the light emittinglayer; the content of the phosphorescent compound in each layer; andrelated emission, are summarized in Table 1.

TABLE 1 Content Content Content A of B of C of PhosphorescentPhosphorescent Phosphorescent or Fluorescent or Fluorescent orFluorescent Compound Compound Compound in Light in Hole in ElectronColor Emission Blocking Blocking Organic of Layer (% Layer Layer B/A ×C/A × EL Emitted by 1 (% by (% by 100 100 Element Light weight) weight)weight) (%) (%) *1 *2 Remarks 1-1 Green 6 0.05 0 0.83333 0 1.2 0 Inv.1-2 Green 6 0 0 0 0 0 0 Comp. 1-3 Blue 6 0.2 0.05 3.33333 0.8333 2.5 0.3Inv. 1-4 Blue 6 0.2 0.05 3.33333 0.8333 2.5 0.3 Inv. 1-5 Blue 6 0 0 0 00 0 Comp. 1-6 White 6 0.6 0.3 10 5 30 11 Inv. 1-7 White 7 0.3 0 4.285710 36 0 Inv. 1-8 White 9 0 0 0 0 0 0 Comp. 1-9 Yellow 6 0.05 0 0.83333 01.2 0 Comp.  1-10 Yellow 6 0 0 0 0 0 0 Comp. *1: (Amount ofphosphorescent emission in hole blocking layer 1)/(Amount ofphosphorescent emission in light emission layer) × 100 *2: (Amount ofphosphorescent emission in electron blocking layer 1)/(Amount ofphosphorescent emission in light emission layer) × 100 Inv.: Inventive,Comp.: Comparative<Evaluation of Organic EL Elements 1-1 to 1-10>

Organic EL Elements 1-1 to 1-10 obtained as above were evaluated asfollows, and the results were shown in Table 1.

(Emission Life)

A period in which an initial emission intensity of an organic EL elementdecreased to half of it was defined as a half-life period (τ0.5) andused as an index of the life of an organic EL element, the emissionintensity being measured by supplying a constant electric current of 2.5mA/cm² at 23° C. in a dry nitrogen atmosphere. A spectroradiometerCS-1000 produced by Minolta Inc. was used for the measurement.

(External Quantum Efficiency)

Electric current of 2.5 mA/cm² was supplied to each organic EL elementat 23° C. in a dry nitrogen atmosphere, and the external quantumefficiency (%) of each sample was measured. The external quantumefficiency (%) was calculated from the date obtained by using aspectroradiometer CS-1000 produced by Minolta Inc.

In Table 2, the emission lives of Organic EL Elements 1-1 and 1-2 wereexpressed by relative values when the emission life of Organic ELElement 1-2 was set to 100; the emission lives of Organic EL Elements1-3 to 1-5 were expressed by relative values when the emission life ofOrganic EL Element 1-5 was set to 100; the emission lives of Organic ELElements 1-6 to 1-8 were expressed by relative values when the emissionlife of Organic EL Element 1-8 was set to 100; and the emission lives ofOrganic EL Elements 1-9 and 1-10 were expressed by relative values whenthe emission life of Organic EL Element 1-10 was set to 100.

TABLE 2 External Emission Life Quantum Yield Organic EL (Relative(Relative Element Value %) Remarks Value %) 1-1 1100 Inventive 110 1-2100 Comparative 100 1-3 1500 Inventive 117 1-4 2000 Inventive 120 1-5100 Comparative 100 1-6 1000 Inventive 115 1-7 900 Inventive 110 1-8 100Comparative 100 1-9 105 Comparative 102  1-10 100 Comparative 100

The results shown in Table 2 revealed that the organic EL elements ofthe present invention exhibited longer emission lives.

Example 2 Preparation of Full Color Displays

(Organic EL Element Emitting Blue Light)

Organic EL Element 1-4 prepared in Example 1 was used.

(Organic EL Element Emitting Green Light)

Organic EL Element 1-1 prepared in Example 1 was used.

(Organic EL Element Emitting Red Light)

Organic EL Element 1-4R, prepared in the same manner as Organic ELElement 1-4 except that Ir-9 was used instead of I-12, was used.

The above blue, green and red light emitting organic EL elements werejuxtaposed on the same substrate to prepare a full color display drivenby an active matrix method, illustrated in FIG. 1. In FIG. 2, aschematic drawing of only display section A is shown. Namely, on thesame substrate, a wiring section containing plural scanning lines 5 andplural data lines 6 and juxtaposed plural pixels 3 (pixels emitting redlight, pixels emitting green light and pixels emitting blue light) areprovided. The plural scanning lines 5 and plural data lines 6 of thewiring section are composed of an electroconductive material. The lines5 and the lines 6 are crossing with each other at a right angle to forma lattice, and connected to the pixels 3 at the crossed points (notillustrated). The plural pixels 3 are driven by an active matrix methodin which each pixel contains an organic EL element emitting acorresponding color light and active elements including a switchingtransistor and a driving transistor. When scanning signals are appliedthrough the scanning lines 5, image data signals are received throughdata lines 6, and emission occurs according to the received image data.By juxtaposing red light emitting pixels, green light emitting pixels,and blue light emitting pixels side by side on the same substrate,display of a full color image was fabricated.

By driving the full color display, it was confirmed that a full colormoving picture with long life was obtained.

Example 3

An illuminator was prepared by covering the non-emitting surface ofOrganic EL Element 1-6 with a glass case. Thus prepared illuminator wasfound to be a thin film white light emitting illuminator exhibiting highluminance, high emission efficiency and long life. FIG. 5 shows aschematic illustration of the illuminator, and FIG. 6 shows across-section of the illuminator.

POSSIBILITY FOR INDUSTRIAL USE

The present invention enables to provide an organic electroluminescentelement, an illuminator and a display, exhibiting long life.

1. An organic electroluminescent element comprising an anode and acathode having therebetween a light emitting layer containing aphosphorescent compound, and a hole blocking layer provided adjacent tothe light emitting layer and between the light emitting layer and thecathode, wherein the hole blocking layer contains a phosphorescentcompound; and a content of the phosphorescent compound contained in thehole blocking layer, in percent by weight, is in the range of 0.1 to 20%of a content, in % by weight, of the phosphorescent compound containedin the light emitting layer.
 2. The organic electroluminescent elementof claim 1, wherein the organic electroluminescent element furthercomprises a second hole blocking layer provided adjacent to the holeblocking layer and between the hole blocking layer and the cathode. 3.The organic electroluminescent element of claim 1, wherein thephosphorescent compound contained in the light emitting layer is thesame as the phosphorescent compound contained in the hole blockinglayer.
 4. The organic electroluminescent element of claim 1, wherein thephosphorescent compound contained in the light emitting layer isdifferent from the phosphorescent compound contained in the holeblocking layer.
 5. An organic electroluminescent element comprising ananode and a cathode having therebetween a light emitting layercontaining a phosphorescent compound, and an electron blocking layerprovided adjacent to the light emitting layer and between the lightemitting layer and the anode, wherein the electron blocking layercontains a phosphorescent compound; and a content, in % by weight, ofthe phosphorescent compound contained in the electron blocking layer isin the range of 0.1 to 20% of the content, in % by weight, of thephosphorescent compound contained in the light emitting layer.
 6. Theorganic electroluminescent element of claim 5, wherein the organicelectroluminescent element further comprises a second electron blockinglayer provided adjacent to the electron blocking layer and between theelectron blocking layer and the anode.
 7. The organic electroluminescentelement of claim 5, wherein the phosphorescent compound contained in thelight emitting layer is the same as the phosphorescent compoundcontained in the electron blocking layer.
 8. The organicelectroluminescent element of claim 5, wherein the phosphorescentcompound contained in the light emitting layer is different from thephosphorescent compound contained in the electron blocking layer.
 9. Anorganic electroluminescent element comprising an anode and a cathodehaving therebetween a light emitting layer containing a phosphorescentcompound; a hole blocking layer provided adjacent to the light emittinglayer and between the light emitting layer and the cathode; and anelectron blocking layer provided adjacent to the light emitting layerand between the light emitting layer and the anode, wherein the holeblocking layer contains a phosphorescent compound; a content in % byweight of the phosphorescent compound contained in the hole blockinglayer is in the range of 0.1 to 20% of the content, in % by weight, ofthe phosphorescent compound contained in the light emitting layer; theelectron blocking layer contains a phosphorescent compound; and thecontent, in % by weight; of the phosphorescent compound contained in theelectron blocking layer is in the range of 0.1 to 20% of the content, in% by weight, of the phosphorescent compound contained in the lightemitting layer.
 10. The organic electroluminescent element of claim 9,wherein the organic electroluminescent element further comprises a holeblocking layer provided adjacent to the hole blocking layer and betweenthe hole blocking layer and the cathode.
 11. The organicelectroluminescent element of claim 9, wherein the organicelectroluminescent element further comprises a second electron blockinglayer provided adjacent to electron blocking layer and between theelectron blocking layer and the anode.
 12. The organicelectroluminescent element of claim 9, wherein the phosphorescentcompound contained in the light emitting layer is the same as thephosphorescent compound contained in the hole blocking layer.
 13. Theorganic electroluminescent element of claim 9, wherein thephosphorescent compound contained in the light emitting layer isdifferent from the phosphorescent compound contained in the holeblocking layer.
 14. The organic electroluminescent element of claim 9,wherein the phosphorescent compound contained in the light emittinglayer is the same as the phosphorescent compound contained in theelectron blocking layer.
 15. The organic electroluminescent element ofclaim 9, wherein the phosphorescent compound contained in the lightemitting layer is different from the phosphorescent compound containedin the electron blocking layer.
 16. The organic electroluminescentelement of claim 1 emitting white light.
 17. A display comprising theorganic electroluminescent element of claim
 1. 18. An illuminationdevice comprising the organic electroluminescent element of claim
 1. 19.A display comprising a liquid crystal cell and the illumination deviceof claim
 18. 20. The organic electroluminescent element of claim 5emitting white light.
 21. A display comprising the organicelectroluminescent element of claim
 5. 22. An illumination devicecomprising the organic electroluminescent element of claim
 5. 23. Adisplay comprising a liquid crystal cell and the illumination device ofclaim
 22. 24. The organic electroluminescent element of claim 9 emittingwhite light.
 25. A display comprising the organic electroluminescentelement of claim
 9. 26. An illumination device comprising the organicelectroluminescent element of claim
 9. 27. A display comprising a liquidcrystal cell and the illumination device of claim 26.